The Receptor for Advanced Glycation Endproducts is a pattern recognition receptor that can be activated by advanced glycation endproducts, members of the S100 protein family or amyloid b (Ab) peptides. Ab oligomers are generated by proteolytic digestion of the amyloid precursor protein (APP) and are currently believed to be the most toxic forms of Ab. We recently showed that Ab oligomers interact preferentially with the V domain of RAGE whereas other forms of Ab (fibrils, aggregates) interact with other domains of the receptor. We showed that engagement of RAGE by Ab oligomers lead to neuronal apoptosis. Blocking the interaction of RAGE by Ab oligomers could lead to significant reduction of neuronal death in Alzheimer's patients. We propose to use single chain monoclonal antibody (light chain) to block RAGE/ Ab interaction. Single chain domain antibodies have been shown to cross the blood brain barrier and are thus promising agents to target and block brain receptors. We have recently generated a Fab fragment antibody phage display library targeting RAGE. Ten selected Fabs reacting with RAGE presented truncated and thus non- functional heavy chains. We could sub-cloned the light chain of truncated Fab B2 into a His tag containing vector and purified it to homogeneity. We showed that the recombinant light chain could bind to RAGE and displace RAGE ligand S100B in vitro. We propose here to further evaluate these single domain light chain antibodies by measuring their binding affinities to RAGE in vitro (ELISA) and on the surface of cells. We will then test the ability of these antibodies to block cell death triggered by the engagement of RAGE by distinct b amyloid oligomeric forms.